Crystallization of tungsten disulfide from molten slags



United States PatentO ABSTRACT on THE DISCLOSURE Crystalline tungsten disulfide is produced by smelting a mixture of sulfide bearing material and tungsten-bearing material in the presence of silica and lime.

This invention relates to the recovery of tungsten from tungsten-bearing materials.

Presentiy employed commercial processes for the recovery of tungsten from ores involve gravity separation or flotation techniques;However, many tungsten ores are difficult to treat inthis manner and the product usually recovered (e.g., scheelite, CaWQ may contain only 30 per cent of the tungsten originally present in the ore. Pyrite (P68) is the'most common interfering mineral in such processes; Y a V 1 It has now been discovered that tungsten can be recoveredfrom tungsten-bearing materials as tungsten disulfide which is readily prepared by smelting tungstenbearing materials with a sulfide-bearing material in the presence of a calcium oxide-silicon dioxide fluxing agent. The fluxing agent acts to free the sulfur from the sulfidebearing material, so that it can react with'the tungstenbearing material to form tungsten disulfide. The molten mass when cooled contains crystalline tungsten disulfide which can be recovered therefrom in substantially pure form" by conventional sulfide flotation techniques. Although t'he tungsten disulfide product has several valuable commercial uses, it can be conventionally reduced to elemental tungsten. It is therefore an object of this invention to provide a dioxide (usually as silica). The total charge is then heated to the melting point of the materials. During the melting,

Tungsten-bearing materiel sulfide-nearing material S10 and Cat) smelting melt containing tungsten disulthe cooling l solidified melt containing crystalline tungsten r disulfide I flotation tungsten disulfide l silicon dioxide basically reacts with the elements (other than tungsten and sulfur) present inthe tungstenand sulfide-bearing materials to form slags whereby the tungsten and sulfur are free to react with one another; and the silicon dioxide also reacts with the CaO to form a calcium silicate slag. An exemplary basic reaction between silica, tungstenand sulfide-bearing materials is as follows: 3 CaWO +7FeS +10SiO 3CaSiO +7FeSiO +SO SW8 The SiO -CaO slag reaction enables the basic reaction to proceed to the right. SiO- should therefore be added in amounts sufficient to release substantially all the tungsten and sulfur present and to react with the CaO. When the S'i0 and CaO form an alpha calcium silicate slag, the most favorable basic reaction is achieved. Such a slag can normally be formed if the CaO and the SiO (above that stoichiometrically required for the basic reaction) are each added in amounts equal to at least about 2.5 percent by weight of the total charge. 7 Operating temperatures during melting depend on the melting point of the particular materials present. After process for more selectively recovering tungsten from difiicult-to-treat tungsten-bearing pres. A further object is to selectively recover tungsten from tungsten-bearing maemploy sulfide-bearing materials, which normally interfere with tungsten recovery processes, as agents for securing a high recovery of tungsten.- i f Other objects and advantages of this invention will be obvious from the .detailed description of the process appearing in the specification taken in conjunction with the following flow diagram in whichthe overall tungsten recovery procedure is shown below. V

In the process of the present invention a tungsten-bearing material, such as a mineral, an ore, or ore concentrate containing tungsten or atungstic oxide is mixed with sulficient sulfide-bearing material, such as pyrite (FeS pyrrhotite (Fe'S), oldhamite '(CaS), other sulfides, or mixtures thereof, to convert all the tungsten present to the disulfide. Added to this mixture as fluxing or slagging agents are calcium oxide (usually as lime) and silicon fusion, slag can be removed from the molten mass, and

the remaining molten product cooled to solidification, or the entire molten mass can be cooled. Solidified melt containing crystalline tungsten disulfide is then ground to minus 100400 mesh for flotation of the sulfide with a conventional sulfide collector and frother. Tungsten disulfide concentrate recovered from the flotation is repulped and floated a number of times (usually twice) to produce the desired purity in the disulfide concentrate.

Among the tungsten-bearing materials that can be treated by the process of this invention are tungsten oxide (W0 or W0 scheelite (CaWOQ, wolframite [(Fe,Mn)WO hubnerite and other tungstic oxide materials.

Many sulfide-bearing materials can be employed including FeNiS, CuS, Cu S, ZnS, PbS, etc. Cost is the main prohibiting factor with regard to the particular material employed.

The following examples illustrate specific ways in which the process can be carried out.

EXAMPLE l 7 reduced to elemental metal, low grade ores, n ow con- The following charges using a scheelite ore concentrate sldemd non'amenable to current P mg techniques, were smelted in an electric furnace at about 1450" c. for would provlde a new raw matenal source r elemental one hour: tungsten.

Basic Reactants, grams Calcium silicate slag reactants, grams Test Temperature, No. Scheelite C.

concen- FeS FeSz CaS SiOz CaO SiOz trate 1 l Schcellte concentrate contained about 50% W or about 77% CaWO; with some heavy mineral impurities (garnet, ilmemte, magnetite, pyrite).

After cooling the solidified melts were then ground to 20 Although the particular process is well adapted to carry minus 200 mesh in a ball mill, pulped at 20 percent solout the objects of the present invention, it is to be underids, and the tungsten disulfide floated with a sodium secstood that various modifications'and changes may be made ondary butyl xanthate collector (used in amounts ranging all coming within the scope of the following claims.

from 0.2 to 1.0 pound per ton) and a water soluble poly- What is claimed is:

propylene methyl glycol ether frothing agent (used in 1. A process for producing tungsten disulfide from a amounts ranging from 0.01 to 0.1 pound per ton of solid tungsten-bearing material comprising P U- Y analyses of thfihlngsten disulfide crystals (a) smelting a mixture of sulfide-bearing material and Showfid essfintiahy 100 Phfceht zsaid tungsten-bearing material in the presence of sili- EXAMPLE 2 con dioxide and calcium oxide, said silicon dioxide being present in an amount sufiicient to release tungsten and sulfur from said materials and sufficient to react with said calcium oxide to form a calcium silicate slag whereby molten slag and molten product A charge consisting of hubnerite concentrate (MnWO pyrrhotite (FeS) and fluxing agents were smelted in a globar furnace at 1450" C. for one hour. The charge consisted of the following:

containing tungsten dlsulfide are formed; B'aslc P Grams (b) cooling said molten product to form a solid prodgubnerfte concentrate not containing crystalline tungsten disulfide. g 33 2. The process of claim 1 further comprising recover- 1 2) ing substantially pure tungsten disulfide from said solid Calcium silicate slag reactants: 4 d b lfid fl Quartz s o 30 0 P Y 511 f 3. The process of claim 1 wherein said tungsten-bear- Lime (CaO) 20 mg material is selected from the group consisting of tung- Qgff giigfggggggggiTg tfizgg533L5 2}; stei-bearing colmpoinds, minerals, ores, ore concentrates an mixturest ereo tals essengally i i concentratlon methods 4. The process of claim 1 wherein said sulfide-bearing were mm at to x'amp e material is selected from the group consisting of pyrite,

EXAMPLE 3 pyrrhotite, oldhamite and mixtures thereof.

Charges of tungsten and tungstic oxide were smelted in Theprocess of claim 1 wherein said ha a. split graphite furnace at from 1500 to 1660 c. for material 18 selected from the group conslstmg of 2.

one hour with the following weights of re ta t d fl W0 scheelite, wolframite, hubnerite and mixtures thereing agents used: of.

Basic Reaetants, grams Calcium silicate slag Test No. reactants, grams Temperature, C. 028 SiOa 6210 $102 30 15 2o 15 1,650 30 15 30 15 1,650 30 15 a0 40 1,650 30 16 a0 39 1,700 30 15 a0 39 1,500

Solidified melt was treated in a similar manner to that 6. The process of claim 1 wherein said sulfide-bearing shown in Example 1. X-ray analyses showed the major material is present in amounts sufiicient to convert sub- Poftioll 0f the tungsten t0 he in the form of tungsten stantially all the tungsten in said tungsten-bearing material disulfideto tungsten disulfide.

Experimental Studies have shown that hlhgshc QXlde 7. The process of claim 1 wherein said silicon dioxide terials will not react with a sulfide-bearing material in the and calcium oxide are gachpresent in the total charge to molten state m the absence of either S10 or CaO. Test said smelting step in an amount- Sufficient to form an alpha results for maximum conversion of the tungsten to tung- 1 1 h 1 calcium sllicate s ag. stetn zg g i that a slag of a P cmm S1 1' 7O 8. The process of claim 3 wherein said silicon dioxide ca 6 gave 6 es rcsu and calcium oxide are each present in the total charge to A high-grade tungsten disulfide meeting commercial requirements is produced by the process of this invention. It is useful as a lubricant or a hydrogenation catalyst for 6310mm slhcate gcarbonaceous materials. Further since it can be readily 9. The process of claim 3 wherein said sulfide-bearing said smelting step in an amount sufficient to form an alpha 5 6 material is selected from the group consisting of pyrite, 2,769,691 11/1956 Achille 23-181 py'rrhotite, oldhamite and mixtures thereof. 3,256,058 6/ 1966 Burwell 23-134 X 10. The process of claim 9 wherein said silicon dioxide and calcium oxide are each present in the total charge to FOREIGN PATENTS said smelting step in an amount sufficient to form an alpha 5 1,155,103 10/1963 Germany; 0 calcium silicate lag Great Blltall'ls 484,329 5/ 1938 Great Britain. References Cited 630,042 10/1949 Great Britain.

UNITED STATES PATENTS EDWARD J. MEROS, Primary Examiner. 1,235,953 8/1917 Bacon 23-131 10 2,120,485 6/1938 Clemrner et a1 23--1s PETERSAssismmExamine 

